Rotary compressor provided with at least one side channel

ABSTRACT

The invention relates to a rotary compressor that includes a disc-shaped rotor having a radius R, supporting on the periphery thereof at least one first series of non-planar blades intended for accelerating the fluid to be compressed between an intake and an outlet, a casing defining on the outside at least one generally toroidal channel that is peripheral to the rotor, said at least one channel being coaxial, arranged at the radial end of said rotor and containing said blades, a static and annular core being arranged inside said at least one toroidal channel such as to define a free section A with said casing. According to the invention, the arrangements and respective shapes of the rotor, the at least one peripheral channel and said at least one series of blades are such that the ratio A/R2 is between 6% and 16%.

TECHNICAL FIELD OF THE INVENTION

The invention relates to the field of volumetric compressors and more specifically volumetric compressors referred to as peripheral or regenerative. These machines are intended to compress a fluid, in particular a gas, between an intake opening (or intake) and an outlet opening (or outlet) in the way of a dynamic compressor.

Many realisations have been known for many years but this technology appears to be promising as decisive improvements can be made to it.

PRIOR ART

The oldest volumetric compressors appeared in the 1950s and they comprise a series of vanes or blades fixed to the end of a wheel-shaped rotor, and which rotate in an annular channel wherein they are mounted with minimum clearance. These machines, contrary to vane compressors, do not require lubrication and the friction therein is reduced. However leaks result from these mountings which furthermore do not offer good output.

The performance of peripheral compressors is between that of vane compressors and that of centrifugal compressors. The aerodynamics of the peripheral compressors is therefore based on the rotation of blades in an annular channel. This results in that the movement imparted to the fluid is a relatively complex helicoidal movement, that induces a compression that is comparable to that of a multi-stage compressor. A high compression rate and low rotation speeds constitute the technical characteristics of this type of compressor.

In the 1970s the shape of the blades of volumetric compressors was modified as well as that of the annular channel in such a way as to improve the centrifugal effect. In particular the blades changed to larger dimensions and more elaborated forms.

An improvement consisted in providing curved blades. U.S. Pat. No. 3,973,865 shows an example of a compressor of this type where the blades have a shape, a material and dimensions intended to reduce the noise created at the intake and at the outlet of the peripheral channel. The output of this type of compressor is of a magnitude of 40% for a flow rate of about 1000 m3/h, and with a compression rate of 1.3 per stage.

A later improvement consisted in setting up an annular element referred to as central core in an annular or toroidal channel arranged laterally to the disc-shaped rotor. The flow in the annular channel then becomes three-dimensional. FIG. 1 diagrammatically shows this type of machine which can be assimilated to a partial injection multi-tiered centrifugal compressor. Outputs of a magnitude of 50% are obtained with this type of machine, having a flow rate of 4000 m3/h and a compression rate of about 1.6. The speeds of the rotor are relatively low, of a magnitude of 100 m/s which decreases the problems of wear and tear on the parts. The low speeds of the rotor furthermore make it possible to use any type of metal for the blades. However this technological evolution did not reach the expected commercial success because the value of the energy output was still insufficient to compete with the highest-performance centrifugal machines; the applications were limited to cases where mechanical simplicity was favoured.

Compressors are also known such as shown in FIG. 2, improvements to those of FIG. 1 because they are provided with several side channels. These compressors can include two so-called side channels because each one is arranged symmetrically on either side of the main plane of the rotor. FIG. 2 shows an example comprising three peripheral channels: two lateral and one radial. Each one of these channels arranged as such has its own intake and outlet orifices. If the outlet of the first channel is associated with the intake of a second channel, the fluid is compressed twice in such a way that the flow rate being that of a single-channel compressor, the compression shall be doubled.

In the case where the compressor has two side channels arranged on either side of the plane of the rotor, the two intakes and the two outlets of the fluid are twinned, which makes it possible to double the flow rate of the compressor.

The digital simulations of such three-dimensional flows of fluids are not very accurate and are digitally limited. Any attempt to simplify via one- or two-dimensional simulations is intrinsically insufficient because the different flows (at the intake, at the outlet, recirculation, tangential, circular) have comparable proportions while still each having significant and hierarchically variable influences for all of the operating speeds.

DESCRIPTION OF THE INVENTION

The invention aims to overcome the disadvantages of prior art and in particular to provide a side-channel compressor of simple design, of which the output is improved; the leaks are furthermore largely decreased and are hardly significant.

To do this a rotary compressor is proposed comprising a disc-shaped rotor having a radius R and supporting on the periphery thereof at least one first series of non-planar blades intended for accelerating the fluid to be compressed between an intake and an outlet, a casing defining on the outside at least one generally toroidal channel that is peripheral to the rotor, said channel being coaxial and arranged at the radial end of said rotor and housing said blades, a static and annular core being arranged inside said at least one toroidal channel in such a way as to define with said casing a free cross section A.

According to a first aspect of the invention, the respective arrangements and shapes of the rotor, of the at least one peripheral channel and of said at least one first series of blades are such that the ratio A/R2 is between 6% and 16%. Furthermore the compressor according to the invention can include a third series of blades arranged in the radial extension of said rotor and inside a given specific channel.

This characteristic dimensioning makes it possible in particular to optimise the compression of the fluid in the compressor. The blades accelerate the fluid according to a movement that is both tangential to the rotor, and perpendicular to this tangential movement. The flow of fluid induces multiple passes of the fluid between the blades, over several loops leading to an improved compression rate and relatively low rotation speeds.

Furthermore said at least one first series of blades has a dimension h measured in parallel to or perpendicular to the axis XX of rotation of the rotor, said dimension h being such that the ratio h/R is between 5% and 15%.

This characteristic aims to improve the output of the compressor.

Advantageously said casing of said at least one peripheral channel and/or said static core has internal reliefs intended to modify the direction of the fluid which flows inside of said peripheral channel, in particular between two juxtaposed blades. A rectifying effect of the flow is here obtained preferentially jointly with the shape of the blades, not planar. This is a conjugated design of the shape of the blades and of the inner wall of the associated channel and/or of the static core.

Moreover a separation part is arranged in said at least one peripheral channel, between the intake and the outlet of said fluid, said separation part having a shape and means that make it possible to progressively lower the pressure of said fluid before his recirculation. Given that the fluid passes several times between the blades before being evacuated from the considered channel, this separation part between the intake and the outlet of the considered channel is important for the proper recirculation of the fluid and in particular with the aim of reducing load losses.

According to an embodiment of the invention, the blades that comprise said at least one first series of blades have a so called circumferential orientation, globally parallel to the axis of said rotor. A second series of blades of the same orientation but arranged symmetrically in relation to the plane of the rotor can be provided without leaving the scope of the invention. Each series of blades is preferentially arranged in an associated specific peripheral channel, defined on the outside by a casing.

Of course each of these embodiments has the dimensional characteristics defined in the header, making it possible in particular to increase the output.

Interestingly, said rotor has a multiplicity of through-holes intended to balance the induced axial pressures.

According to another characteristic of the invention, the compressor comprises at least one intake stub pipe for the fluid, that exits into said at least one peripheral channel and directs therein said fluid in a direction opposite or perpendicular to the direction of rotation of said rotor.

When several peripheral channels are provided, the latter can have different or identical cross sections. Those skilled in the art will choose according to the constraints associated to the case under consideration.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics, details and advantages of the invention shall appear when reading the following description, in reference to the annexed figures, which show:

FIGS. 1 and 2 correspond to arrangements of compressors known to which the invention is applied;

FIG. 3 is a diagrammatical section showing certain dimensional relations characteristic of the invention;

FIG. 4 is a cross-section of a peripheral channel wherein the main flows can be seen;

the three diagrams of FIG. 5 relate to a ratio characteristic of the invention;

the three diagrams of FIG. 6 relate to another ratio characteristic of the invention;

FIG. 7 is a flat view of a peripheral channel with the stream of associated flows; and

FIG. 8 is a flat view of a peripheral channel with the stream of associated flows.

For increased clarity, identical or similar elements are marked with identical reference signs over all of the figures.

DETAILED DESCRIPTION OF AN EMBODIMENT

The diagrams of FIGS. 1 and 2 relate to compressors that are respectively provided with a side channel and three peripheral channels, two lateral and one radial. Of a structure known per se, these compressors are part of the invention from the moment when characteristic dimensional radii are provided.

In a known manner therefore, such compressors comprise a wheel or circular disc-shaped rotor 1 having a radius R, to which a series of blades 2 is attached. The series of blades can consist of a set of non-planar blades 2 that have a so called circumferential orientation i.e. in a plane that is more or less close to a circumference of the rotor 1. FIG. 3 diagrammatically shows this option. In this same figure has been shown the casing 3 of the rotor 1 which substantially hugs the shape of it while still arranging an axial clearance corresponding to areas of leakage and load losses.

Preferentially but not necessarily the rotor 1 has a set of through-holes 30 intended to balance the various induced axial pressures.

The blades 2 are housed in an annular channel 4 in the shape of a torus which moreover houses a static core 5 that is also annular and coaxial to the rotor 1. The annular channel 4 is advantageously coaxial to the rotor 1 and it is qualified as ‘peripheral’ as it is arranged at the radial end of the rotor 1.

As already mentioned, other peripheral channels can be provided, arranged symmetrically with regards to the main plane of the rotor 1 or at the distal and radial end of the rotor 1.

The flow of the fluid in the channel or channels 4 is three-dimensional and complex. FIG. 4 shows via a cross-section of one of the channels 4, the breakdown of the flow from the intake 10 of the fluid in the channel 4 to its outlet 20. A flow referred to as circulatory d is generated, coming from the passage between the blades 2. This is a helicoidal flow which causes the fluid to flow several times through the blades 2 before exiting at the outlet 20. A flow referred to as tangential c is also created, laminar on the inner wall of the channel 4. This flow is created by the blades 2 and its slowing down inside the annular channel 4 creates the pressure in the compressor.

In the intermediate zone between the intake 10 and the outlet 20 of a channel 4, a flow e referred to as recirculation is created. A separation part 6 is in particular provided with holes 60 that, associated with its specific shape, make it possible to lower the pressure of the fluid which will recirculate between the outlet 20 and the intake 10. The arrows f and g of FIG. 4 respectively symbolise the prior leaks and the post leaks.

The invention relates to ratios A/R2 where A is the surface area of the cross-sectional area of the passage of at least one of the peripheral channels, and where R is the radius of the rotary wheel 1. The surface area A therefore globally corresponds to the section of passage offered to the fluid to travel through the channel, from the intake 10 to the outlet 20. Interestingly and surprisingly, it was found that a ratio A/R2 between 8% and 16% makes it possible to optimise the output of the compressor.

FIG. 5 shows several ratios that enter into the scope of the invention. With an equally-sized rotor 1 and blade 2, the size of the free channel 4 can therefore vary in proportions characteristic of the invention. It is the dimensions of the blades 2 that, at equal size, make it possible to be in a configuration according to the invention. The clearance (distance) between the blades 2 and the core 5 can be constant or not.

Moreover it has been found that the width h of the blades 2 relatively to the radius R of the rotor 1 must remain in proportions such that h/R is between 5% and 15%. Width here means the dimension of a blade 2 measured either parallel to or perpendicular to the axis XX of rotation of the rotor 1; parallel in the case where the blades are oriented circumferentially to the axis XX of the rotor as shown in FIG. 1, 3, 5 or 6; perpendicularly to the axis XX in the case of blades oriented according to the main plan of the rotor 1.

This characteristic is particularly interesting to increase the performance of the compressor by decreasing the relative share of the leaks.

As can be seen diagrammatically in FIG. 4 an intake duct 11 exits into the channel 4 with a preferred orientation; this orientation must be different from the perpendicular to the plane of the rotor 1. An orientation of the intake stub pipe 11 in the retrograde direction of the wheel shall preferentially be chosen, i.e. in opposition to the direction of rotation of the wheel 1.

In the vicinity of the intake 10 the average helicoidal flow of the fluid in the channel 4 is disturbed, all the more so that the intake orifice 10 is large. The larger the dimension of the intake orifice 10 is, the lower the dimension of the channel 4 effective for the compression will be.

It is moreover preferred to place the intake opening 10 underneath the core 5, for example as shown by the square 4 in FIG. 1. Concerning the outlet opening 20, it is placed preferentially above the core 5 i.e. at a point noted 1 in the square of FIG. 1. The orientation of the outlet stub pipe 21 associated with the opening 20 will be quasi tangential, highly progressive (according to the direction of rotation of the rotor). It is as such sought to minimise the load losses and induce a movement close to that of the average flow.

The FIG. 7 is a flattened view showing the progression of the fluid in a peripheral channel, more particularly the flow between the blades 2 and around the static core 5, from the intake 10 to the outlet 20 of the channel. The graphs at different points of the flow correspond to the total speed of the fluid combining the circulation around the core (ordinates) according to its progression between the intake 10 and the outlet 20 (abscissa) at certain points of the channel 4.

This entails rectifying the flow during the passing from one blade to the juxtaposed blade. To do this, the shape of the blades 2 is important and it shall therefore be chosen as non-planar.

It is also preferred, in order to further rectify the flow between two blades 2, to provide reliefs such as grooves or deflectors in the inside wall of the casing of the channel or on the wall of the core 5. FIG. 8 diagrammatically shows the effects of this characteristic intended to optimise the flow from the outlet of a blade to the intake on the following blade. This entails optimising the speeds and the pressures at each point of the flow and reducing the losses through turbulence between two different zones of pressure in order to reduce their variations during the passage between two blades.

Other modifications can be made by those skilled in the art without leaving the scope of the invention. In particular when several peripheral channels are provided, their respective dimensions are not necessarily equal; the surface areas A of each channel considered can be different; however each surface area A satisfies in particular the ratio A/R2 characteristic of the invention.

The compressor according to the invention reaches adiabatic efficiencies of approximately 60%. Many types of gas can be used according to the invention: pure, corrosive, explosive or flammable gases. The pressure variation can reach 40 bars and the compression rate can exceed 3. This performance is hardly affected by the operating conditions. For the purposes of information, the intake pressure can reach a value of up to 200 bars with a temperature of a magnitude of 200° C., a flow rate of 60,000 Nm3/h. The rotation speeds are low, of a magnitude of 100 m/s. The seals used can be carbon seals. Such a compressor is economical because it requires reduced maintenance, low dimensions and low installation costs. The lubrication system is very simple to implement and, contrary to centrifugal compressors no anti-surge system is required.

The applications considered relate for example to the production of natural gas: the invention can be integrated into a regeneration circulator of a drier screen. With regards to cogeneration, the compressors according to the invention can for example be used to supply GTs.

Other applications relate to biogas blowers, blowers used in various industrial methods, oxygenation for fish farming, lyophilisation etc. 

1. Rotary compressor comprising a disc-shaped rotor having a radius R and supporting on the periphery thereof at least one first series of non-planar blades intended for accelerating the fluid to be compressed between an intake and an outlet, a casing defining on the outside at least one generally toroidal channel that is peripheral to the rotor, said at least one channel being coaxial, arranged at the radial end of said rotor and housing said blades, a static and annular core being arranged inside of said at least one toroidal channel in such a way as to define with said casing a free cross section A characterised in that the dispositions and respective forms of the rotor, of at least one peripheral channel and of said at least one first series of blades are such that the ratio A/R2 is between 6% and 16% and in that it comprises a third series of blades arranged in the radial extension of said rotor and in a given specific channel.
 2. Rotary compressor according to claim 1 characterised in that said at least one first series of blades has a dimension h measured parallel to or perpendicular to the axis XX of rotation of the rotor, said dimension h being such that the ratio h/R is between 5% and 15%.
 3. Rotary compressor according to claim 1 characterised in that said casing of said at least one peripheral channel/or said static core has reliefs intended to modify the direction of the fluid that flows inside said peripheral channel in particular between two juxtaposed blades.
 4. Rotary compressor according to claim 1 characterised in that it comprises a separation part arranged in said at least one peripheral channel, between the intake and the outlet of said fluid, said separation part having a shape making it possible to progressively lower the pressure of said fluid before the intake of the fluid.
 5. Rotary compressor as according to claim 1 characterised in that the blades that comprise said at least one first series of blades has a so-called circumferential orientation, globally parallel to the axis of said rotor.
 6. Rotary compressor according to claim 1 characterised in that it comprises two series of blades arranged symmetrically on either side of the main plane of said rotor, each series being arranged in a specific peripheral channel.
 7. Rotary compressor according to claim 1 characterised in that said rotor has a multiplicity of through-holes intended to balance the induced axial pressures.
 8. Rotary compressor according to claim 1 characterised in that it comprises at least one intake stub pipe for the fluid, that exits into said at least one peripheral channel and directs therein said fluid in a direction opposite or perpendicular to the direction of rotation of said rotor.
 9. Rotary compressor according to claim 1 characterised in that it comprises several peripheral channels that have free cross sections A with different values. 